Add a special case to not render anything if the method parameter to the math helper is a template to match the official DustJS implementation.

src/renderer/renderer.rs

@@ -5,6 +5,7 @@ use crate::parser::Filter;
 use crate::parser::OwnedLiteral;
 use crate::parser::PartialNameElement;
 use crate::parser::Path;
+use crate::parser::RValue;
 use crate::parser::Special;
 use crate::parser::Template;
 use crate::parser::TemplateElement;
@@ -675,8 +676,13 @@ impl<'a> DustRenderer<'a> {
 
                         // Generate a ParametersContext with the result of the math operation as key
                         let converted_value: BreadcrumbTreeElement<'_> = calculated_value.into();
-                        let calculated_param_map: HashMap<&str, Option<BreadcrumbTreeElement<'_>>> =
-                            vec![("key", Some(converted_value))].into_iter().collect();
+                        let dummy_rvalue = RValue::RVLiteral(OwnedLiteral::LPositiveInteger(0));
+                        let calculated_param_map: HashMap<
+                            &str,
+                            (&RValue<'_>, Option<BreadcrumbTreeElement<'_>>),
+                        > = vec![("key", (&dummy_rvalue, Some(converted_value)))]
+                            .into_iter()
+                            .collect();
                         let calculated_context =
                             ParametersContext::from_values(None, calculated_param_map);
                         // calculate are_any_checks_true
@@ -982,6 +988,21 @@ impl<'a> DustRenderer<'a> {
         breadcrumbs: &'a Vec<BreadcrumbTreeElement<'a>>,
         math_parameters: &'a ParametersContext<'a>,
     ) -> Option<IceResult<'a>> {
+        // Special case: if method is a template then do not render
+        // anything. This is to match the behavior of dustjs even
+        // though it works fine.
+        match math_parameters.get_original_rvalue("method") {
+            Some(RValue::RVTemplate(template)) => {
+                if template.iter().any(|pne| match pne {
+                    PartialNameElement::PNReference { .. } => true,
+                    PartialNameElement::PNSpan { .. } => false,
+                }) {
+                    return None;
+                }
+            }
+            _ => (),
+        }
+
         let method = match self.tap(breadcrumbs, math_parameters, "method") {
             None | Some(Err(_)) => return None,
             Some(Ok(ice_result)) => ice_result,